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Author Topic: Brushless ESC amp to brushless Moror amp  (Read 545 times)

Mr Johnty

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Brushless ESC amp to brushless Moror amp
« on: August 02, 2022, 01:35:10 pm »

Hi all.Bought some things for my tug boat yesterday dont know if i have made an error or not can someone please advise?I have a NiMH 1,800 mah battery and a brushless 40amp ESC i have only just noticed that the brushless motor i have bought is 47amp.Is this a huge problem as its only in a tug 1/30 scale and the motor wont be creaming only a nice slow spin. %% Hope its not going to be aproblem but i know you guys on here will tell me if it is. <:( Many thanks
John
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captain_reg

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Re: Brushless ESC amp to brushless Moror amp
« Reply #1 on: August 02, 2022, 05:59:58 pm »

Hi John


Could do with a bit more info to give a better answer. What is your battery voltage and what is the make & model of your ESC & motor?


I've not come across many motors that specify a fixed definite amperage as this varies massively with what you do with it, as you say you won't be creaming it  :}  I've always been a big fan of a bathtub test with an amp meter to prove out any spec sheet info.


It might be me thinking of brushed motors but is your 47amps the stall current? If it is then you're unlikely to every see this in reality and a 30amp fuse will nicely protect everything. For comparison I've got a Speed 700 that will pull 43Amps stalled but pulls less than 10 at full throttle with a 45mm prop attached.


Richard
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Mr Johnty

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Re: Brushless ESC amp to brushless Moror amp
« Reply #2 on: August 02, 2022, 06:50:48 pm »

Hi Rchard.Info you asked for .ESC Ripmax Quantum 40amp brushless.Motor is a Robotbird gs b36-56-06 1800kv brushless inrunner.Battery is a Radient superpax 3s 11.1v 1800mah 30c.Hope this is helpful to you. John

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captain_reg

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Re: Brushless ESC amp to brushless Moror amp
« Reply #3 on: August 02, 2022, 07:26:30 pm »

Ah yeah, they don't really specify on their website what that current figure is for. I had a look at a few other similar motors on the same site and they all have vastly different amounts of info specified, one had both power & max current whilst some were just blank.


I've only really just started the transition from brushed to brushless myself so I'm sure someone with more experience will give you a definite answer. I'd assume that 47amps is the maximum or in other words stall current. So as long you don't over do it I think you'll be fine. Fuses are always best practice  :-))


One thing that does jump out, are you planning to use a reduction gearbox with the motor? Tugs have never been my thing but it 1800kv seems like quite high rpm for a tug. I don't think it will be too happy trying to drive a big tug style 50mm prop at 20,000 rpm


Hope this helps.
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chas

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Re: Brushless ESC amp to brushless Moror amp
« Reply #4 on: August 02, 2022, 11:27:45 pm »

Hi John, your motor is 1800 kv, that's 1800 revs per volt, with your battery you'll get near 20,000 revs at the prop.  Generally a tug will run from a couple of hundred revs to two or three thousand, and drive a biggish prop. Sorry mate, that motor isn't suitable, it might be great in a fast speedboat, but not in a tug.

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Mr Johnty

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Re: Brushless ESC amp to brushless Moror amp
« Reply #5 on: August 03, 2022, 08:59:17 am »

Hi Chas.Thanks for that info .
Not the news I was hoping for realy.Can you advised what sort of notor I need or is a reduction gearbox the answer.Again what gearbox would I need turning out to be a minefield this . :(( John
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JimG

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Re: Brushless ESC amp to brushless Moror amp
« Reply #6 on: August 03, 2022, 11:37:32 am »

I've only really just started the transition from brushed to brushless myself so I'm sure someone with more experience will give you a definite answer. I'd assume that 47amps is the maximum or in other words stall current. So as long you don't over do it I think you'll be fine. Fuses are always best practice  :-))

Hope this helps.
The 47 amp is the maximum recommended current for the motor, while it can take a higher current if overloaded it will rapidly overheat and may cause damage. One feature of a brushless motor is there is no real stall current, if the motor is fully stalled the current will drop to zero. I've just tested a brushless motor, normal full power current is around 25A, Stopping the motor from turning it initially pulsed trying to move with a current around 4A max then stopped responding with a current of zero. This is the esc responding to the lack of feed back showing the motor is turning. Basically a brushless doesn't need a fuse as it will not take a very high current when staled unlike a brushed motor where it is a near short through the coils when stalled. The only use for a fuse would lbe if the esc fails internally creating an short circuit, this is a very rare event, normally it lets he smoke out and stops working.
Jim
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JimG

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Re: Brushless ESC amp to brushless Moror amp
« Reply #7 on: August 03, 2022, 11:46:47 am »

Hi John, your motor is 1800 kv, that's 1800 revs per volt, with your battery you'll get near 20,000 revs at the prop.  Generally a tug will run from a couple of hundred revs to two or three thousand, and drive a biggish prop. Sorry mate, that motor isn't suitable, it might be great in a fast speedboat, but not in a tug.
My ST Cruiser uses a brushless of around 900kV with a 3S battery, prop size is 50mm 4 blade. On full power it is well overpowered although well within the motors limits, I do have the esc set to reduced power, around 60% to give a more scale speed but with plenty left for emergencies or towing. (Motor was originally out of a plane using a 6s pack turning a large scale 3 blade airscrew so running on 3s is way less than it can handle.) If th power is a bit much then you do have the option of the throttle stick to keep it slower.
Jim
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chas

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Re: Brushless ESC amp to brushless Moror amp
« Reply #8 on: August 03, 2022, 12:32:14 pm »

This is all getting a bit back to front. To estimate a suitable motor, we need to know the size of the model, 30 scale can mean a whole range of sizes, because tugs vary hugely. An idea of the weight would help, and very importantly the prop size you are using.
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NickelBelter

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Re: Brushless ESC amp to brushless Moror amp
« Reply #9 on: August 03, 2022, 01:39:49 pm »

I believe he has the Ulises tug, which has a prop somewhere between 35 and 50mm diameter.  In that case, an outrunner around 500-600kv should work just fine. 
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chas

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Re: Brushless ESC amp to brushless Moror amp
« Reply #10 on: August 03, 2022, 03:47:11 pm »

Thanks nickelBelter,, I know the ulises very well, there are a couple in our club. Both are running on 540 LN motors from MFA, with mtronics esc, and NiMH batteries, they have ample power, and would be fine with a 3s lipo. If staying with brushless something around the 500 kv as you say would be perfect, but might cost more than the brushed motor and esc I've mentioned.
  I expect many people already know that the LN version of the 540 is completely different from other versions, and is designed for lower rev slogging.
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Mr Johnty

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Re: Brushless ESC amp to brushless Moror amp
« Reply #11 on: August 03, 2022, 04:42:36 pm »

Hi All.And thanks for all the fantastic information.But im still very confused i know the motor i have is far to fast for what i need and NickelBelter has said to get a 500-600kv outrunner motor.Also chas ahs said that perhaps 540 LN motors from MFA.What i need to know is if i get a 500-600kv outrunner can i still use the other things i have ie. ESC Ripmax Quantum 40amp and my Radient superpax NiMH  3s 11.1v 1800mah 30c battery.?? If the ESC and battery are fine to use i will just get a new smaller motor.If its just a case of smaller motor can anyone recomend any makes models please.
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unbuiltnautilus

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Re: Brushless ESC amp to brushless Moror amp
« Reply #12 on: August 03, 2022, 11:14:56 pm »

Unless you are prepared to hunt down a very low Kv motor (krick do their MAX MarineP359 350Kv motor, but at about forty quid a bit of a specialised option), I would fit the RE540LN motor and a Quicrun 1060 speed control, total cost about 32. Keep the brushless speed control for the next project. You can get a 500Kv motor, but most of them are in the 50 size range, which roughly translated is a big old beast that will barely fit in a Ullyses Tug.
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chas

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Re: Brushless ESC amp to brushless Moror amp
« Reply #13 on: August 04, 2022, 11:26:46 am »

Hi Johnty  unbuiltnautilus has it spot on. A suitable low kv brushless will probably cost more than the 540LN and a speed controller, and be too bulky. All I can add is that when you use a lipo with a standard esc, it's worth buying a low voltage alarm to plug into the balance lead. I got one for about three quid, and it can save your battery from being over discharged and ruined.
Chas

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